Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing the new design.

The outermost broken line rectangle illustrates a display screen orportion thereof and forms no part of the claimed design. The remainingbroken lines illustrate portions of the graphical user interface thatform no part of the claimed design.

CLAIM We claim the ornamental design for a display screen or portionthereof with a graphical user interface, as shown and described.